After reading all the post here and those at other sites (including those for SLK's ) this seems to be a well documented failure. However, I have yet to find one where the root cause has been ID'ed. I also experienced while driving my '07 ltd roadster the "Air Bag, ABS & BAS/ESP fault lights illuminating and the Spoiler extending. This resulted in the red pilot light in the manual Spoiler control switch to begin blinking. Pressing the spoiler switch did not retract the spoiler as it normally should have. After turning off the engine and turning the key to the run position, the spoiler switch pilot lite was no longer blinking and pressing it retraced the spoiler. Starting the engine showed the Air Bag fault light no longer lit, but the ABS & BAS/ESP still on. The next day when I started my XF the fault lights where no longer illuminated and all appeared normal. After a short drive the fault once again appeared. Now, after turning the engine off and waiting a few minutes before turning the key to the run position the spoiler can be retracted resulting in the Air Bag light going off, but the ABS & BAS/ESP fault lights remaining on.

My OBD scanner lacks the ability to read the type of faults set by Air Bag, ABS, BAS/ESP, et al so my next step will to find a reasonable priced alternative to obtain them.

If anyone has found the root cause we they be so kind as to share with the rest of us.